The present invention relates to an integrated circuit device, its manufacturing method, a circuit board and a method of manufacturing the same.
A monolithic IC having an active element such as a transistor and a passive element such as a resistor, a capacitor or an inductor integrated on a semiconductor substrate is low in manufacturing cost, permits suppressing the power consumption, and can be miniaturized, and thus, the monolithic IC can be formed as a one chip.
However, where an inductor is formed on a semiconductor substrate, a parasitic capacitance and a parasitic resistance (eddy current loss) are generated between the conductor forming the inductor and the semiconductor substrate. Therefore, in order to obtain an inductor having a high Q factor, it is necessary to lower the parasitic capacitance and the parasitic resistance.
As a method for lowering the parasitic capacitance and the parasitic resistance, proposed is a method of forming an inductor above a groove formed on the surface of a semiconductor substrate. To be more specific, it is proposed in, for example, U.S. Pat. No. 5,539,241, that an inductor is formed in an air-floating wiring structure so as to increase the distance between the inductor and the semiconductor substrate and, thus, to lower the parasitic capacitance and the parasitic resistance.
In the conventional structure exemplified above, however, it was impossible to ensure a sufficient mechanical strength because the inductor is floating in the air.
It is also proposed to form an active element such as a transistor and a passive element such as a capacitor or an inductor on different substrates, followed by bonding these elements by using a bump, as disclosed in, for example, ISSCC98/SESSION 16, DIGEST OF TECHNICAL PAPERS, pp 248-249.
However, the substrate having an active element formed thereon and the substrate having a passive element formed thereon are arranged such that the element-forming surfaces are allowed to face each other. It follows that the semiconductor substrate having, for example, a transistor formed thereon is apart from the inductor by only a distance determined by the bump. As a result, it was difficult to lower sufficiently the influence of the semiconductor substrate having the transistor formed thereon.
Also, a circuit board having a conductive connecting portion formed within an insulating layer is known to the art. In the conventional technology, however, it is difficult to control the shape of the conductive connecting portion, and the step for forming the conductive connecting portion is made complex.